Q.

The wavelength of spectral line obtained in the spectrum of Li2+ ion, when the transition takes place between two levels whose sum is 4 and difference is 2, is            [2026]

1 2.28×10-7 cm  
2 2.28×10-6 cm  
3 1.14×10-6 cm  
4 1.14×10-7 cm  

Ans.

(3)

n1lower energy level

n2higher energy level

n1+n2=4,  n2=3

n2-n1=2,  n1=1

Rydberg's formula:

1λ=RHZ2[1n12-1n22]

1λ=RH(3)2[112-132]

1λ=8RH

λ=18RH

λ=18×1.1×105

λ=10008.8×10-8 cm

λ=113.63×10-8 cm

λ1.14×10-6 cm